Hi,just joined to say thanks for the skilled repair info I fixed my first board (shinobi system 16a bootleg) using your post on page 1 (Troubleshooting CPS 1 audio problems). I've read here or somewhere these Cps1 boards are based on the sega system 16 hardware,so i thought i'd follow your advice,even though there not the same boards

I carefully ran thru your guidelines,everything kinda checked out to my unskilled eyes. Then i got to the YM2151,tested the IRQ,RD,WR with my logic probe,they were stuck high,so i cut out the on board Z80A,solder suckered the holes,installed a 40 pin socket,and stuck my newly acquired sharp Z80A cpu in,fired it up and to my surprise it worked

There's a huge sense of satisfaction in bringing a dead system back to life!

If that Z80A dies again, replace it with a Z80B - The B version is what should be used in the System 16 boards as they run pretty fast.

Raymond

Thanks,i'll check that out,if i have any problems with this one.I still got three spare,got'em from ebay cause they were cheap and new.I was wondering about that at the time i ordered the Z80A,but i thought maybe thats why they used a Z80A in place of the Z80.I dont wanna ruin these,so i'll deff replace it at some stage.Also replaced a couple of caps on it too,there was a broken resistor on the top right of the board,which maybe took out the cap right next to it,dunno! It checked out bad on my blue esr meter anyway.The resistor was the cause of a few graphics glitches,but they cleared right up when replaced.Cheers again man,that was the clearest and most concise info i could find,great for us noobs ; ) Found some info about op amps,but that just didn't check out.Great resource ; )

The resistor probably didn't cause any issues with the cap. Old caps dry up and their ESR rating goes up.

The funny thing is that many caps that test bad on an ESR meter will show right on a capacitance meter. It goes to show that you can't just rely on a cap meter when working on monitors, boards, power supplies, etc... places where a bad cap will cause strange issues. If the ESR reading is off, replace the cap.

You did it by the book there with your ESR meter! Most people don't even have one but it's indispensable for working on boards. I bought the older model kit from Anatek and have used it a lot over the years. I'm cheap so I couldn't see myself spending 150+ on an ESR meter when the $80 kit would work just as well for my needs.

Oh, and one other thing you should look at when troubleshooting audio issues on a Sega System 16 type board... They use these funny looking small plastic cased rectangular crystals on the board for the D/A playback chip. They are typically orange or blue in color and are easy to break off the board. If you get a board that is missing some sounds such as the speech or digitized sound effects look to see if that clock crystal is broken off the board.

I know what you mean,im cheap too .I got the blue esr meter in kit form on ebay,from a guy in the uk.Cost me 70 euros plus postage,didn't think that was too bad.

Got another board with sound problems,it has in game sound effects but no music.But i think thats related to the op amps.Kinda fudged that one up a bit,trying to take off a part that looked dodgy.Soldering iron didn't get hot enough and i pulled the via out of its hole with the part,trying to save it,should of just cut it out in hindsight.So i gotta somehow fix the via,then get to the op amp.When i pulled the via,i think it pulled about a mil or two all around of the trace inside the hole,so i think i need to widen the hole to get at the trace inside now Wouldn't mind but i bought the board working,played it a couple of times and the music just fizzled out one day.Dunno about fixing other boards just yet,this ones knocked me back a bit.But i'll get to it some time Then later i'll prob need to pick up a eeprom programmer,and a scope and learn how to use them first

Before the scope, I'd recommend a logic probe with audio capabilities. That way you can look at the signals coming out of the audio chips to make sure they are there before going into the op-amps. The audio capabilities lets you "hear" (albeit in a 2 tone hi/low distorted logic probe sound) the outputs.

If not that, then an audio probe. Those will be much cheaper than a scope.

It's easy to repair the traces since the only things on the inner layers of that board are power and ground. Pick up a small spool of 30ga Kynar wire wrap wire and a small bottle of non-metallic green nail polish. Use the wire to bridge the missing trace and use the polish to tack it down to stay.

ok ok thanks , i will try to do what you told me ....but not sure i wil find where are the pins 69 pin71 of the neo C1 chip ;-(i hope i will find out tomorrow when i will check what you told me today ;-0

thanks for your personal answer too channel maniac

don't you think it wil be good to show for everybody a picture of one board and show what exactly each IC is doing for the board ? for exemple YM for the sound ...IC7425 control the 6 buttons ..etc Cause i read so much your post and sometimes iam losing with all you tell and some IC i don't know for what they are doingi have around 20 boards ( most are F1SZS now and i tryed to repair , before i payed for that but bad work and very expensive so i decide to ''try '' to resolve alone so iam a rookie and not so easy too

hard to understand why anyone would put $$$ in old neo geo board when you can buy a 1 slot new board for around 100 bucks and buy a game cartage with 100 games for same cost

Because a typical board repair runs between $45 to $55 plus shipping... and with the repair you know what you are getting.

Used Neo Geo boards may have bad caps in the audio section or leaking batteries just the same as ones that are being repaired. A repair service brings the board up to being fully functional. Additionally folks may want to keep the 2, 4, or 6 slot board in the cabinet as that is what it was designed for and what the marquee is for.

Some of the Neo Geo cabinets also have memory card slots and headphone jacks on the front which will be empty if you replace the board with a simple 1 slot - especially a 1 slot board with no support for an external memory card/headphone board that is used on a 4 or 6 slot cabinet.

I suppose I could state the same thing about some slot games. hehehehehe!

wow, those do not sound like easy fixes at all, with the exception of maybe the 2 player not working. Sounds like you are very talented at what you do! I sent ya a PM on the Neo Geo forums for some help on Psikyo board I'm working on fixing with BustedStr8 right now

I just wanted to say thank you for putting up your Neo Geo repair logs. Had I not gone through them, I would have been pulling hairs chasing a non-existent "Watchdog" issue.

I repaired another bad MV4F top board I acquired that had trace damage due to improper shipping precautions (seems to be a common problem with the MVS boards I have...). The bottom board however rapidly clicked through the speakers when powered up and the screen display would flicker in unison.

I started probing the AS745 chips and after not finding anything conclusive, I re-read the repair logs and found an issue you previously encountered which had the exact same symptoms. I then thought to hit the Player 1 button and saw that the board wasn't reseting at all.

As I was checking things out in the audio section just as you had, I noticed that the 12V capacitor was "ballooned". I really don't know why, but I touched the capacitor and gave myself a 1st degree burn on my fingertip just to confirm what was plainly obvious at this point... For lack of parts on hand, I swapped an existing capacitor from an audio channel with the 12V capacitor and everything minus the right audio channel came up fine.

Since I started pulling capacitors off the board, I figured I'd order a cap kit and do the rest of the audio caps as well.

Again, thank you very much! Now I just need to figure out what I'm going to do with two extra mainboards...

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